Yutaka Sawamukai

Rakuno Gakuen University, Ebetsu, Hokkaidō, Japan

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Publications (24)18.66 Total impact

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    ABSTRACT: This study reports a viable means of identifying the vitellogenic cycle and limited estrus period in hawksbill turtles for the purposes of developing captive breeding program, based on the combination of blood metabolite parameters (triglyceride, total protein, and calcium levels), feeding status, and ovary condition. Follicle size of two focal captive females showed clear seasonal changes, with major development occurring between March and May (19.0-24.4 mm), and exceeding 25 mm between June and September. Triglyceride, total protein, and calcium levels dropped with follicular development and maintenance (March to October), and then began to rise when follicular retraction occurred from October onwards. The two focal turtles reduced food intake during intensive follicular development (April to May). These findings suggest that blood metabolite parameters and feeding conditions are inferred by the vitellogenic cycle. An additional 10 females exhibiting follicular development were mated with a single male for 7-day period between May and June. Follicle size was measured immediately prior to pairing, and a statistically significant difference in follicle size of 10 females was recorded between the seven failed (20.9 mm) and three successful (23.6 mm) mating events. This indicates follicle development is essential to successful mate and monitoring of vitellogenic cycle may help improve the success rates of captive hawksbill breeding programs.
    No preview · Article · Feb 2015 · ZOOLOGICAL SCIENCE
  • Isao Kawazu · Konomi Maeda · Masanori Koyago · Ken Nakada · Yutaka Sawamukai
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    ABSTRACT: This study presented information about the semen evaluation of captive male hawksbill sea turtles, Eretmochelys imbricata, based on an extended 15-mo study using the electro-ejaculation technique. In particular, we demonstrated that hawksbill sperm, which is underactive just after ejaculation, was activated by the presence of urine. The findings are useful for developing optimal semen collection techniques for future artificial insemination programs of hawksbill turtles.
    No preview · Article · Dec 2014 · Chelonian Conservation and Biology
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    ABSTRACT: We set out to develop an oviposition induction technique for captive female hawksbill turtles Eretmochelys imbricata. The infertile eggs of nine females were induced to develop by the administration of follicle-stimulating hormone, after which we investigated the effects of administering oxytocin on oviposition. Seven of the turtles were held in a stationary horizontal position on a retention stand, and then oxytocin was administrated (0.6-0.8 units/kg of body weight; 5 mL). The seven turtles were retained for a mandatory 2 h period after oxytocin administration, and were then returned to the holding tanks. As the control, normal saline (5 mL) was administered to the other two turtles, followed by the administration of oxytocin after 24 h. The eggs in oviducts of all nine turtles were observed by ultrasonography at 24 h after oxytocin administration. The control experiment validated that stationary retention and normal saline administration had no effect on egg oviposition. Eight of the turtles began ovipositing eggs at 17-43 min after oxytocin administration, while one began ovipositing in the holding tank immediately after retention. All turtles finished ovipositing eggs within 24 h of oxytocin administration. This report is the first to demonstrate successful induced oviposition in sea turtles. We suggest that the muscles in the oviducts of hawksbill turtles may respond to relatively lower doses of oxytocin (inducing contractions) compared to land and freshwater turtles (4-40 units/kg) based on existing studies.
    No preview · Article · Dec 2014 · ZOOLOGICAL SCIENCE
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    ABSTRACT: To develop ovulation induction techniques, we investigated the effects of follicle- stimulating hormone (FSH) administration on ovulation in captive hawksbill turtles Eretmochelys imbricata. Porcine FSH preparation was administered by intramuscular injection to four hawksbill turtles with fully-developed follicles (21.6–23.8 mm, measured using ultrasonography) in July or August 2009. Blood samples were obtained and subjected to plasma progesterone measurement, and ovaries and oviducts were observed by ultrasonography just before, and 1–6 days after, FSH administration. One day after the administraion, the plasma progesterone concentration significantly increased from the basal level (<0.01–0.3 ng/mL) to 0.8– 5.1 ng/mL and then dropped to nearly the basal level within 2–4 days. The formation of eggshells was observed two days after FSH administration. These data collectively indicate that in hawksbill turtles FSH administration effectively induces ovulation, progesterone secretion, and egg formation.
    Full-text · Article · Feb 2014 · Current Herpetology
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    ABSTRACT: Blood estrone sulfate (E(1) S), estrone (E(1) ), estradiol (E(2) ) and progesterone (P(4) ) in newborn piglets were measured to clarify the relationships among birth and placental weight, vitality of offspring and litter size. First, the association between vital status (normal, weak and stillborn) from 165 newborn piglets of 18 litters and steroid concentrations; second, steroid concentrations from 152 newborn normal piglets and litter size; and third, steroid content in fetal placenta from 50 newborn normal piglets of six litters and litter size, were investigated. In the normal group, the birth and placental weight were significantly higher than those in the other groups. Blood E(1) S levels in the stillborn group were significantly lower, whereas E(1) , E(2) and P(4) were significantly higher compared to the normal group. Blood and placental E(1) S levels in the small litter group were significantly higher than those in the other groups. However, there was no significant difference among the three litter size groups in the levels of steroid hormones in maternal blood. These results indicate that vitality of newborn piglets is related to E(1) S concentration of neonate, to birth weight and placental weight. However, steroid hormone concentrations of newborn piglets were greatly affected by the number of littermates.
    No preview · Article · Sep 2012 · Animal Science Journal
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    ABSTRACT: To clarify the physiological changes of sperm morphology in active Thoroughbred stallions during the breeding season, we examined the dismount semen collected from the penile urethra immediately after service. The spermatozoa were analyzed for relationships between the morphology and the stallion’s age or the number of services. Seasonal variation was apparent in the rate of the sperm tail abnormalities, spermatozoa with cytoplasmic droplets, appearance of medusa cells, and sperm head length. Area and width of the sperm head correlated negatively with age (P<0.05). The rate of appearance of medusa cells and the length of the sperm head were positively related to the number of services (P<0.05), and the aspect ratio was negatively related (P<0.01).
    Preview · Article · Apr 2009 · Journal of Equine Science
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    ABSTRACT: The morphology of spermatozoa of modern Thoroughbred stallions in Japan was investigated during the breeding season. A total of 299 semen samples were collected from the penises of 16 stallions immediately after service. The rate of abnormalities in sperm heads and tails, spermatozoa with cytoplasmic droplets and slides with medusa cells to total observed slides in each stallion were 3.9 +/- 2.1%, 11.5 +/- 5.9%, 2.4 +/- 2.6% and 20.1%, respectively. The values for the area, length, width and aspect ratio of the stallion sperm head were 12.54 +/- 1.34 microm(2), 5.93 +/- 0.40 microm, 2.69 +/- 0.21 microm and 0.46 +/- 0.05, respectively. With the exception of medusa cells, the features were significantly different among the stallions (P<0.05).
    Preview · Article · Oct 2008 · Journal of Veterinary Medical Science
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    ABSTRACT: A total of 88 thoroughbred mares were diagnosed with clinical ovarian quiescence and subjected to four treatment regimens. Using PMSG, hCG or combinations of both. A high dose combination of 5,000IU PMSG with 5,000IU hCG showed significantly higher rates of marked estrus and ovulation induction (P<0.01) as well as conception rates (P<0.05). In the present study, the administration of a high-dose combination of PMSG with hCG was shown to be an effective treatment of ovarian quiescence in light mares.
    Preview · Article · Jul 2008 · Journal of Equine Science
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    ABSTRACT: The concentrations of androstenedione, estradiol-17β, progesterone and PGF2α contained in the follicular fluid produced by the follicles in collected ovaries of mares that have had estrous phase during the breeding season were measured and analyzed the relation between the growth stage of follicles and the hormone levels in the follicular fluid. An ultrasonographic diagnostic instrument was used to measure the diameter of the follicles in order to categorize the follicles into three groups the following: 8 small follicles (from 1.0 to less than1.5 cm), 8 medium follicles (from 1.5 to less than 3.0 cm), and 8 large follicles (from 3.0 to 5.0 cm), respectively. The analysis of the follicular fluid in ovaries of estrous mares showed that the concentrations of androstenedione were significantly higher in the medium or large follicles than in the small follicles and the concentrations of estradiol-17β were significantly higher in larger follicles than in the small or medium follicles (P<0.05). The concentrations of progesterone and PGF2α, on the other hand, did not significantly vary regardless of follicluar size. In the follicles within the mare ovaries that have had estrous stage, the concentrations of the hormones related the ovulation, namely androstenedione and estradiol-17β, were higher with larger follicles.
    Preview · Article · Jul 2008 · Journal of Equine Science
  • T. Tsukada · A.Y. Kojima · M. Moriyoshi · M. Koyago · K. Sato · Y. Sawamukai
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    ABSTRACT: The effect of perfusion of hCG, PGF2α, vasoactive peptides, and Ringer&apos;s solution (control) on the ovaries of mares (Percheron, Breton and crossbred) during early and functional luteal phases of the ovarian cycle was studied using an in vitro microdialysis system. There was no increase in P4 secretion as a result of the perfusion of 10 IU or 100 IU of hCG during the early or functional luteal phase. But both the levels of hCG significantly increased PGF2α release, compared to the control, during early luteal phase (p<0.05). During functional luteal phase, 100 IU hCG caused significantly higher secretion of PGF2α than 10 IU hCG or the control (p<0.05). P4 release was significantly higher than in the control (p<0.05) with PGF2α perfusion in both the early and the functional luteal phases. Vasoactive peptides (angiotensin-Ⅱ, endothelin-Ⅰ and atrial natriuretic peptide) did not cause a significant difference in P4 release during the early or the functional luteal phase. However, PGF2α release was significantly increased compared to the control (p<0.05) in both phases. These results suggest that hCG and vasoactive peptides had a profound effect on PGF2α release but did not stimulate P4 secretion during the early or the functional luteal phase in equines.
    No preview · Article · Jan 2008
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    ABSTRACT: Reproductive diseases after parturition are a serious problem in dairy cattle. It is important to predict postpartum reproductive diseases early and to develop prophylaxis. The objectives of this study were to demonstrate changes in the peripheral blood concentration of interleukin-6 (IL-6) before parturition, which was mainly produced by T helper 2 type (Th2) cells, and to investigate a correlation between the IL-6 concentration and the occurrence of the postpartum retained placenta, endometritis and/or follicular cyst in dairy cattle. Twenty-seven Holstein-Friesian cows were used for this study. Thirteen had no clinical disease, 8 had retained placenta, 4 were diagnosed with endometritis by vaginal inspection, and 2 were diagnosed with follicular cyst by rectal palpation at 1 and 2 months after parturition. Blood samples were collected 60 days pre- and post-partum. They used for IL-6, progesterone (P(4)) and estradiol-17beta (E(2)) concentration determination. This study showed that the IL-6 concentration prepartum was higher than postpartum. Low levels of IL-6 and P(4) in peripheral blood prepartum tended to affect retained placenta and a high level of IL-6 prepartum tended to affect endometritis. These results indicate that measurement of change in the IL-6 concentration during pregnancy is one useful tool for predicting crisis in postpartum reproductive diseases in dairy cattle.
    Full-text · Article · Dec 2004 · Journal of Veterinary Medical Science
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    ABSTRACT: Reproductive diseases after parturition are a serious problem in dairy cattle. It is important to predict postpartum reproductive diseases early and to develop prophylaxis. The objectives of this study were to demonstrate changes in the peripheral blood concentration of interleukin-6 (IL-6) before parturition, which was mainly produced by T helper 2 type (Th2) cells, and to investigate a correlation between the IL-6 concentration and the occurrence of the postpartum retained placenta, endometritis and/or follicular cyst in dairy cattle. Twenty-seven Holstein-Friesian cows were used for this study. Thirteen had no clinical disease, 8 had retained placenta, 4 were diagnosed with endometritis by vaginal inspection, and 2 were diagnosed with follicular cyst by rectal palpation at 1 and 2 months after parturition. Blood samples were collected 60 days pre- and post-partum. They used for IL-6, progesterone (P4) and estradiol-17β (E2) concentration determination. This study showed that the IL-6 concentration prepartum was higher than postpartum. Low levels of IL-6 and P4 in peripheral blood prepartum tended to affect retained placenta and a high level of IL-6 prepartum tended to affect endometritis. These results indicate that measurement of change in the IL-6 concentration during pregnancy is one useful tool for predicting crisis in postpartum reproductive diseases in dairy cattle.
    No preview · Article · Nov 2004 · Journal of Veterinary Medical Science
  • M Miyoshi · Y Sawamukai
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    ABSTRACT: The objective of this study was to evaluate the distribution and phagocytotic function of macrophages in bovine caruncles during pregnancy. Pregnant Holstein caruncles obtained at a slaughterhouse and by Caesarean section just before the onset of parturition were used. Macrophages in these caruncles were observed immunohistochemically and histochemically. Macrophages were present in the parenchyma of caruncles throughout pregnancy. The macrophages were irregular in shape, and exhibited thin, long processes along the main and intermediate septa of caruncles. Macrophages increased as the gestation period progressed. Acid phosphatase activity of the macrophages appeared at 5-6 months of gestation and remained until the end of gestation period. In particular, macrophages showed strong acid phosphatase activity at the peripheral region of the caruncles just facing the chorionic villi. In addition, they were conglomerated in the hyperplastic prominences of caruncles. These results indicate that caruncle macrophages maintain the appropriate size and shape of each caruncle during pregnancy.
    No preview · Article · Jul 2004 · Reproduction in Domestic Animals
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    ABSTRACT: A new method for catheterization of the portal and hepatic veins in cattle by means of the over-the-wire system was investigated to maintain more reliable long-term patency of catheters. Four cattle were used to evaluate the success rate, patency and safety of the procedure. The catheters, coated by urokinase were patent as long as they were in situ. In addition, the introducer was useful to prevent the catheter from being broken. No complications developed during the10 days after the procedure. Two cows were then euthanized. Post mortem findings were minimal. The results of the study reported here are promising, the benefits are significant and there is no apparent disadvantage to its use.
    No preview · Article · Aug 2003 · Journal of Veterinary Medical Science
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    ABSTRACT: We investigated the therapeutic effects of a progesterone releasing intravaginal device (PRID) on cystic ovarian disease (COD) and reproduction performance of cows. The possible influence of PRID on metabolic and/or health status was also examined. A total of 40 Holstein-Friesian cattle, with ovarian cystic structures, > or =2.5 cm in diameter, persisting for more than 7-14 days, without a corpus luteum (CL) were used for the study. PRID or placebos were inserted into the vagina for 12 days. Five animals lost the intravaginal device before removal and one was culled. Based on plasma progesterone concentration on the day of treatment, 20 (17 PRID and 3 placebos) of the remaining 34 cows had follicular cysts (progesterone < or =1 ng/ml) and 14 (10 PRID and 4 placebos) had luteal cysts (progesterone >1 ng/m l). Fourteen (82%) of the PRID-treated follicular cystic cows responded with formation of a CL within 14 days after treatment, and an overall conception rate of 53.8%. Likewise, 70% of the treated luteal cystic cows responded with CL formation and 71.4% conception rate. No significant differences were observed in hematocrit (Ht), white blood cell count and serum levels of glucose, blood urea nitrogen, aspartate aminotransferase, and alanine aminotransferase, between the day of PRID insertion and removal, in animals with follicular and luteal cysts. PRID treatment resulted in ovulation 2-4 days later and formation of a CL in cows that recovered.
    No preview · Article · Jan 2003 · Journal of Veterinary Medical Science
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    ABSTRACT: The present study was carried out to determine the efficacy of replacing the second GnRH with hCG (GnRHPGF2αhCG) in Ovsynch used for timed AI in cows. In the firstexperiment, Holstein cows were divided into 3 groups according to post-estrus day: day 5-6, day 10-11, and day 15-16 (n = 5 for each group). In each group, ovulation was highly synchronized in cows treated with GnRH-PGF2α-hCG (hCG: 3, 000 IU). In thesecond experiment, Holstein cows were randomly divided into 2 groups and each cow was treated with either GnRHPGF2α-hCG (n=42) or Ovsynch (n=41). Conception rates were 52.4% for cows treated with GnRH-PGF2α-hCG and 51.2% for cows treated with Ovsynch. It was estimated that replacisng GnRH with hCG for ovulation synchronization saved \703 per cow and Y1, 533 per conception. These results show that ovulation synchronization and timed AI for dairy cows can be performed without conception-rate reduction and at lower costs by replacing the second GnRH with hCG in Ovsynch.
    Preview · Article · Jan 2003
  • Ken NAKADA · Yukikazu ISHIKAWA · Toshihiko NAKAO · Yutaka SAWAMUKAI
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    ABSTRACT: This study was carried out to investigate changes in pituitary response to GnRH on gonadotrophin secretion in prepubertal heifers. A total of 50 prepubertal Holstein-Friesian heifers were treated with 1 mug/kg GnRH intravenously at 1, 2,4,6 and 8 months of age, and plasma samples were collected from the jugular vein at 0 to 360 min after GnRH treatment. Plasma concentrations of LH and FSH were measured by RIA. Increase in concentrations of LH and FSH, induced by GnRH, were observed in all heifers from 1 month of age, and the concentrations of LH and FSH at 30 min after GnRH treatment were significantly greater than those before GnRH treatment in heifers of all ages. The time from the GnRH administration to the appearance of the peak of LH and FSH rise was similar at each age and, was prolonged with age. The peak concentration and the amount of release from the pituitary of LH rise increased with age, while those of FSH had a tendency to decrease with age. These results indicate that the pituitary gland already has reactivity to GnRH in heifers by 1 month of age, that the capacity of LH release to GnRH in the pituitary gland develops with age, and that the regulatory mechanism for the secretion of LH and FSH develops differently in prepubertal heifers. This study suggests that the development of the capacity to secrete LH secretion in response to GnRH in the pituitary gland before puberty is one of the factors for deciding the time of the onset of puberty in heifers.
    No preview · Article · Dec 2002 · Journal of Reproduction and Development
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    ABSTRACT: The relationship among nutritional status, systemic insulin-like growth factor-I (IGF-I) and ovarian function early postpartum were investigated. A total of 27 Holstein-Friesian cows, 10 that cycled normally within 20 days postpartum, 5 diagnosed with follicular cysts, 8 with persistent corpus luteum (CL) after the first ovulation postpartum and 4 with inactive ovaries were used for the study. Blood samples were collected 1-3 times per week, for 60 days pre- and postpartum, for IGF-I, progesterone, estradiol, free fatty acids (FFA), blood urea nitrogen (BUN), and aspartate aminotransferase (AST) determination. Inactive ovary and cystic cows had a higher body condition score before calving and lost more condition than normal or persistent CL cows. Immediately postpartum, IGF-I levels were higher and rose sharply in cows that cycled normally than in cystic, inactive ovary or persistent CL cows. At calving and early postpartum, FFA was higher in inactive ovary and cystic than in normal and persistent CL cows. There was a significant strong positive relationship between IGF-I and BUN, and strong negative relationships between IGF-I and FFA and AST in all groups. There was a positive relationship between serum IGF-I and estradiol in normal cystic and inactive ovary cows. This study found that overconditioned cows during the dry period or at calving, lost more body condition postpartum. These cows also had a deeper and longer period of negative energy balance (NEB), poor liver function and low circulating IGF-I concentrations early postpartum. Such cows were likely to have poor reproductive function as seen in development of cystic ovaries, persistent CL and inactive ovary. Changes in serum IGF-I early postpartum may help predict both nutritional and reproductive status in dairy cattle.
    No preview · Article · Nov 2002 · Journal of Veterinary Medical Science
  • Victor Chisha Zulu · Toshihiko Nakao · Yutaka Sawamukai
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    ABSTRACT: The current review aims to establish insulin-like growth factor-1 (IGF-I) as the factor that signals nutritional status to the reproductive axis, and show that assessment of IGF-I in blood early postpartum during the negative energy balance (NEB) period could be used to predict both nutritional and reproductive status in dairy cattle. The review also explores the effect of nutritional status on circulating IGF-I concentrations and the endocrine role of IGF-I on the reproductive axis. IGF-I plays an important role in gonadotropin-induced folliculogenesis, ovarian steroidogenesis and corpus luteum (CL) function. It also modulates pituitary and hypothalamus function. IGF-I clearly has an endocrine role on the reproductive axis. Severe under nutrition significantly reduces plasma IGF-I concentrations. During the critical period of NEB in high yielding dairy cattle early postpartum, IGF-I concentrations are low in blood and its levels are positively correlated to energy status and reproductive function during this period. Changes in circulating IGF-I immediately postpartum may help predict both nutritional and reproductive status in dairy cattle. IGF-I is therefore one of the long sought factors that signal nutritional status to the reproductive axis.
    No preview · Article · Sep 2002 · Journal of Veterinary Medical Science
  • M Miyoshi · Y Sawamukai · T Iwanaga
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    ABSTRACT: This study was carried out to investigate the distribution of immune cells in the bovine placenta during the postpartum period and to compare these cells between normal and retained placenta. Within 1 h after normal calving, biopsy samples of placentomes were collected from 10 cows. The occurrence of retention of fetal membranes was monitored for more than 8 h post-calving, and the samples obtained were divided into two groups: normally discharged and retained placenta (n = 5 each). Immunohistochemical procedures were utilized to detect macrophages and T lymphocytes. Numerous CD14-positive macrophages were found in the stroma of both normal placenta and retained placenta whereas only a few CD3-positive T lymphocytes were found in both cases. However, histochemical staining for acid phosphatase, a predominant lysozomal enzyme, revealed that almost all macrophages showed strong enzyme activity in the normally discharged placentas, whereas in retained placenta the activity of acid phosphatase was conspicuously decreased in intensity. These results indicate that there are functional differences in placental macrophages between normal and retained placenta.
    No preview · Article · Mar 2002 · Reproduction in Domestic Animals